There are four transformations you need to know. Each moves or resizes a shape in a specific way, and each requires a precise description to earn full marks.
Translation — slides a shape without rotating or reflecting it. Describe with a column vector $\binom{x}{y}$ where $x$ is right/left and $y$ is up/down.
Reflection — flips a shape in a mirror line. Describe by stating the equation of the mirror line (e.g. $y = x$, $x = 2$).
Rotation — turns a shape about a fixed point. Describe with: angle, direction (clockwise or anticlockwise), and centre of rotation.
Enlargement — scales a shape from a centre point. Describe with: scale factor and centre of enlargement. A fractional scale factor makes the image smaller; a negative scale factor places the image on the opposite side of the centre.
When asked to describe a transformation, give all required information — a partial description (e.g. "rotation" without angle or centre) scores zero.
Common error: giving two transformations when a single one is asked for — one transformation only.